H. A. Malhat

A Single-Feed Cylindrical Superquadric Dielectric Resonator Antenna for Circular Polarization

Circularly polarized superquadric dielectric resonator antenna is investigated. A single coaxial probe is used to excite circularly polarized patterns. Finite element method is used to analyze the problem. Different aspect ratios of the superquadric dielectric resonator cross section for each squareness parameter for circular polarization are calculated.

Curved dual- band dielectric resonator tag antenna for RFID applications

This paper presents a new application of dielectric resonator antenna in radio frequency identification system. A curved dual-band dielectric resonator antenna for RFID applications is proposed. The tag antenna is designed to operate at 2.45 GHz (2.25– 2.55 GHz) and 5.8 GHz (5.65– 5.95 GHz) bands. The radiation characteristics of the tag antenna in free space are investigated. The radar cross sections under different loads are obtained. The effect of curvature on the tag antenna performance is explained. Two examples are considered. In the first example, the tag antenna is mounted on cylindrical bottle filled with the Polyethylene material. The effect of the object properties on the radiation characteristics and the radar cross section is investigated. In the second example, the tag antenna is mounted on spherical bottle filled with the Polyethylene material. The radiation and backscattering characteristics are calculated. The Finite Element Method (FEM) is used for simulation and the Finite Integration Technique (FIT) is used to verify the simulated results.

DIELECTRIC RESONATOR ANTENNA MOUNTED ON A CIRCULAR CYLINDRICAL GROUND PLANE

In this paper, the radiation characteristics of the single- element cylindrical dielectric resonator antenna mounted on the surface of a metallic hollow circular cylindrical structure is investigated. The efiect of the radius of curvature on the return loss, input impedance, standing wave ratio, and radiation pattern is explored. Mutual coupling between two identical cylindrical dielectric resonator antennas on a cylindrical structure in difierent conflgurations is determined. To reduce the mutual coupling between the two antennas, the surface of the cylinderical ground plane is defected by cutting slots, or inserting quarter wavelength grooves between the two antennas. The flnite element method and the flnite integration technique are used to calculate the radiation characteristics of the antenna.

Graphene Based Transmitarray for Terahertz Applications

Circularly polarized graphene based transmitarray for terahertz applications is proposed. The characteristics of the graphene material is explained. The cell element of the transmitarray is made of square Quartz cell. Dual circular graphene rings are printed on both sides of the Quartz substrate. The graphene ring radius is varied to change the transmission coe-cient phase and magnitude. The efiect of the graphene chemical potential on the transmission coe-cient is demonstrated. Transmitarray is composed of 9 £ 9 unit cell elements. A circularly polarized circular horn is used to feed the transmitarray at f = 6THz. The left- and right-hand fleld components in the E- and H-plane are determined. The variation of the gain and the axial-ratio with the frequency are explained. The peak gain is 18.63dB and 1-dB gain bandwidth is 6.8%. The transmitarray produces a circular polarization from 5.5THz to 6.5THz.

Octafilar helical antenna for handheld UHF RFID reader

Octafilar helical antenna (OFHA) is proposed for handheld ultra-high-frequency (UHF) radio frequency identification (RFID) reader. The investigated antenna configuration consists of OFHA placed on reader device in the presence of human hand model. The antenna is designed at UHF band centred at 915 MHz. The antenna return loss, axial ratio, gain, co-polarized and cross-polarized field components are calculated using the finite element method (FEM) and compared with that calculated by finite integration technique (FIT) for verification of the simulated results. A comparison between the performance of the quadrifilar helical antenna (QFHA) and the octafiliar helical antenna (OFHA) designed at 915 MHz in the presence of the reader device and human hand model is investigated. The OFHA introduces high gain, high front to back ratio, good axial ratio and omnidirectional coverage.

Dielectric Resonator Antenna Reflectarrays Mounted on or Embedded in Conformal Surfaces

Abstract—In this paper, reflectarrays mounted on or embedded in cylindrical and spherical surfaces are designed, analyzed, and simulated at 11.5GHz for satellite applications. A unit cell consists of a square dielectric resonator antenna (DRA) mounted on or embedded in metallic conformal ground plane is investigated. The radiation characteristics of the designed reflectarrays are investigated and compared with that of planar reflectarray. A 13×13 planar reflectarray antenna on the x-y plane was designed. By varying the length of the DRA element between 2 mm and 6.2 mm a full range from 0◦ to 360◦ phase shift can be obtained. The size of each element is equivalent to a compensation phase shift. A maximum directivity of 24.3 dB was achieved while the side lobes were below −12.94 dB in E-plane and −15.79 dB in the H-plane for planar reflectarray. A Full-wave analysis using the finite integration technique (FIT) is applied. The results are validated by comparing with that calculated by transmission line method (TLM).

Circular Polarized Dielectric Resonator Antenna for Portable RFID Reader Using a Single Feed

A new design of circular polarized elliptical dielectric resonator antenna (DRA) with single feed for handheld radio frequency identification (RFID) reader is presented. The elliptical dielectric resonator antenna with an aspect ratio of 1.5 is used. This design has achieved 66.7 MHz impedance bandwidth (for S11 < –10 dB) by using material with dielectric constant material (εr = 12) in conjunction with coaxial probe feed in free space. The DRA models are simulated using two different numerical techniques, the finite element method and the finite integral technique. The numerical results of the two different computational methods approache are investigated and compared. The results are in good agreement within the desired frequency band, 5.65 GHz – 5.95 GHz. A model for a handheld RFID reader device including the elliptical DRA in the presence of human hand models is, also, investigated. The return loss is <10 dB over the frequency range of 5.49– 6.967 GHz resulting in frequency bandwidth of 1.47 GHz. A high front to back ratio and gain of 5.726dBi are obtained.

B10. Multilayer dielectric resonator antenna transmitarray for near-field and far-field fixed RFID reader

A design of multilayer dielectric resonator antenna transmitarray for fixed RFID reader applications is presented at 5.8 GHz. Three layered square DRA element mounted on dielectric substrate is used as a unit cell. The dimensions of the unit cell and the number of layers are optimized to give phase distribution of the transmission coefficient from 0 to 2π. A circularly polarized 9×9 square DRA transmitarray is designed at 5.8 GHz for far-field RFID applications. The transmitarray produces maximum gain of 20.2 dB with 1 dB bandwidth of 1.4 GHz. A design of 9×9 near-field focused DRA transmitarray for fixed RFID at 5.8 GHz is investigated. The properties of the NF-focused transmitarray are compared with the far field transmitarray designed at the same operating frequency. The 3-dB spot area radius of the NF-focused transmitarray aperture is 7.84 cm at the focal plane z =Ro=40 cm with SLL of -17.6 dB.

PERFORATED NANOANTENNA REFLECTARRAY

This paper presents a design of perforated nanoantenna re∞ectarray. The use of metallic nanostructures made of Silver and/or Gold at appropriate wavelength cause fascinating unusual electromagnetic efiects. Re∞ectarray consists of an array of unit cell made from Silver is investigated. The efiect of the number of perforated holes in the unit cell conflgurations is investigated for proper re∞ection coe-cient phase compensation. A linearly polarized pyramidal nano- horn is used to feed the perforated nanoantenna re∞ectarray. The radiation characteristics of 9 £ 9 perforated nanoantenna re∞ectarray are illustrated. A high gain of 20.5dB is obtained at the designed frequency of 735THz. A comparison between solid Silver sheet with no perforation holes and the proposed perforated re∞ectarray is explained.

Circularly polarized graphene based transmitarray for terahertz applications

Circularly polarized graphene based transmitarray for terahertz applications is proposed. The characteristics of the graphene material is explained. The cell element of the transmitarray is made of square Quartz cell. Dual circular graphene rings are printed on both sides of the Quartz substrate. The graphene ring radius is varied to change the transmission coefficient phase and magnitude. The effect of the graphene mobility on the transmission coefficient is demonstrated. Transmitarray is composed of 9×9 unit cell elements. A circularly polarized circular horn is used to feed the transmitarray at f=6 THz. The left- and right-hand field components in the E-and H-plane are determined. The variation of the gain and the axial-ratio with the frequency are explained. The peak gain is 18.63 dB and 1-dB gain bandwidth is 6.8%. The transmitarray produces a circular polarization from 5.5 THz to 6.5 THz.